It is the object of this proposal to study the immunogenicity and tolerogenicity of mouse transplantation antigens, the nature of the immune response directed against them, and their genetic control. The research plan will utilize the following outline: 1. The genetic control of transplantation antigens; a. The completion of production of new congenic strains. b. Selection of new alleles from new congenic lines. c. Detection of non-H-2 specificities using histogenetic and serologic techniques. 2. The immune response to transplantation antigens: a. Completion of time-dose studies of the cellular response to viable lymphocytes bearing transplantation antigens. b. Time-dose studies using subcellular antigen. c. Humoral response to non-H-2 antigens. Production and detection of non-H-2 antibodies. 3. The immunogenic and tolerogenic properties of papain-solubilized transplantation antigen using histogenetic techniques: a. Completion of studies on immunogenicity of various fractions of solubilized transplantation antigen. b. Completion of studies of the immunogenic completeness of ammonium sulfate fraction. c. Production of tolerance using soluble transplantation antigens.